Waves in a simple inhibitorily coupled network of PIR neurons

A network of neurons is coupled via GABA_A synapses. Each "cell"
has only three currents: (i) a passive leak current; (ii) a low threshold
inactivating calcium (T) current and (iii) the synaptic current.

Figure 1A In this figure, the coupling
between cells is localized with a maximum at zero distance and the
waves show a characteristic lurching appearance. A brief localized
stimulus is given to initiate the wave. This leaves clustered activity
in the wake of the wave.

Figure 2A This is identical to the
previous figure except that there is a gap in the coupling so
that cells that are within a small distance of the presynaptic cell do
not receive any input from that cell. The result is smooth
propagation to the left and lurching to the right. Periodic wave
trains are left in the wave of the wave.

Figure 3B
This is identical to Figure 2, except the recovery is slower and the
synaptic kinetics are faster so that re-excitation of the medium is
prevented.

Figure 4 Here the reversal potential of the synsapse is slowly changed in order
to switch the medium from a slow rebound wave to a fast excitation
front. The sign of the near shunting synapse changes from inhibition
to excitation with only a few millivolts difference. A localized
stimulus is given intermittently to excite the middle of the medium.